Python BFS solution


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        m = len(grid)
        if m == 0:
            return 0
        n = len(grid[0])
        q=[]
        for i in range(m):
            for j in range(n):
                if grid[i][j] == 1:
                    q.append((i,j))
        
        res = 0
        directions = [[0,1],[0,-1],[1,0],[-1,0]]
        while q:
            r, c = q.pop(0)
            #upper
            for direct in directions:
                newr = r+direct[0]
                newc = c+direct[1]
                if newr < 0 or newc < 0 or newr >=m or newc >= n:
                    res+=1
                elif grid[newr][newc] == 0:
                    res+=1
        
        return res

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